Flyback converter for virtual series photovoltaic DPP system

Abstract

The invention discloses a flyback converter for a virtual series photovoltaic DPP system. The flyback converter comprises m input circuits, one output circuit and one multi-winding high-frequency transformer; the function of the flyback converter is equal to that of m independent flyback converters which are connected in series; m different input circuits adopt phase shift control; the equivalentswitching frequency of the transformer is m times of the frequency of a switching tube, and meanwhile, the switching loss and the size of the converter are reduced; and when power mismatch exists between different photovoltaic cell panels, the multi-input single-output flyback converter disclosed by the invention can ensure that each photovoltaic cell panel operates at the respective maximum powerpoint, and only one secondary side is connected with the photovoltaic cell panel in series, so that the unification of high power acquisition rate and high efficiency is realized.

Description

technical field [0001] The invention relates to the technical field of power electronic converters and controls, in particular to a flyback converter applied to a virtual series photovoltaic DPP system. Background technique [0002] At present, the mainstream form of photovoltaic use is centralized power generation, which is to connect photovoltaic panels in series and parallel to obtain a photovoltaic array. After ensuring a sufficiently high output voltage and current, the maximum power point tracking is performed by a high-power centralized grid-connected inverter ( MPPT) and grid-connected control, this method has obvious advantages, that is, the topology and control are simple, and the cost is relatively low. But there are also obvious disadvantages, that is, the extremely wide range of input voltage requires the use of devices with high withstand voltage and high on-resistance, and the DC voltage utilization rate of the subsequent inverter is low, resulting in low inve...

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Problems solved by technology

But there are also obvious disadvantages, that is, the extremely wide range of input voltage requires the use of devices with high withstand voltage and high on-resistance, and the DC voltage utilization rate of the subsequent inverter is low, resulting in low inverter efficiency; in addition, Due to the influence of factors such as partial shading, photovoltaic panel installation angle deviation, dust, and electrical parameter differences, the voltage and current at the output maximum power point (MPP) of each photovoltaic panel in the photovoltaic array cannot be consistent, resulting in the output power of the photovoltaic array. Limited by the photovoltaic module with the smallest power, this phenomenon is called power mismatch. In severe cases, the power loss can reach more than 30%. Long-term operation will cause hot spots on the photovoltaic module and burn the module

[0003] Common methods to solve the problem of centralized power generation include photovoltaic DC modules (also known as photovoltaic optimizers) and photovoltaic AC modules (also known as photovoltaic micro-inverters). , but there are also the following problems: both the DC module and the AC module adopt a two-stage circuit structure, and the two-stage conversion is a full power converter (FPP), resulting in complex control, low efficiency, and high cost

However, the photovoltaic cells are connected in parallel, and the DPP converter is connected in series with the photovoltaic cells. Even if there is no power mismatch between the photovoltaic cells, the current of the photovoltaic cells will flow through the DPP converter connected in series with the photovoltaic cells, and every Each battery board is equipped with a DPP converter, resulting in a large series loss

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